Add "shevy" for vertical rhythms

[vwochnik]

Shevy (kyleshevlin/shevy) is really good. I am using it for three websites now.

[tandavas]

Thank you for the suggestion! However, I think we will pass with this one. It would be really nice if it got examples and demo for people to see. That would help a lot.

[vwochnik]

I have talked to the author and due to your suggestions he has created a new website containing a documentation and examples. Therefore, I'd like you to add this library to the list.

[tandavas]

Cool! Can you please send a pull request for this?